Controlled peristaltic pump

ABSTRACT

In peristaltic pumps, using a number of mobile occluding organs which press a resilient hose against a support and which cause the advance of a medium within this hose, an additional support is provided from the limit point of occlusion up to the last contact point with the hose. The distance of the support from the track of the occluding organs being in inverse proportion to the required speed of advance of the medium in this hose.

ilnited States Patent 11 1 Hrdina [451 Sept. 11, 1973 1 CONTROLLEDPERISTALTIC PUMP [75] Inventor: Jii'l' Hrdina, Praha, Czechoslovakia[73] Assignee: Cskoslovenska akademie vecl, Praha,

Czechoslovakia [22] Filed: Dec. 21, 1971 {21] Appl. No.: 210,371

[30] Foreign Application Priority Data Dec. 23, 1970 Czechoslovakia8746/70 [52] HS. Cl. 417/477 [51] Int. Cl. F04b 43/08, F04b 43/12, F04b45/06 [58] Field of Search 417/474, 475, 476, 417/477 [561 ReferencesCited UNITED STATES PATENTS 3,597,124 8/1971 Adams 417/477 3,628,891Isreeli et a1. 417/476 X lsreeli 417/477 X 3,137,241 6/1964 3,101,6748/1963 Weiskopf et al.. 417/477 X FOREIGN PATENTS OR APPLICATIONS467,288 6/1937 Great Britain 417/477 1,119,170 4/1956 France 417/477Primary Examiner-Al Lawrence Smith Assistant Examiner-Richard E. GluckAttorneyRichard Low and Murray Schaffer [57] ABSTRACT In peristalticpumps, using a number of mobile occluding organs which press a resilienthose against a support and which cause the advance of a medium withinthis hose, an additional support is provided from the limit point ofocclusion up to the last contact point with the hose. The distance ofthe support from the track of the occluding organs being in inverseproportion to the required speed of advance of the medium in this hose.

6 Claims, 6 Drawing Figures PATENTED SEW W H SHEET 1 BF 3 A DR "LYPATENTED I 75 SHEET 2 OF 3 FIG. 3

INVENTOR J H R D 1 N L] BYW S- Q (:ZTORNEY PATENTED 1 m3 sum 3 OF 3 WINVENTOR dlm #RJMNA WYTSJZZQY A ORN CONTROLLED PERISTALTIC PUMPBACKGROUND OF THE INVENTION This invention relates to a method and to anarrangement for regulating and programming of the discharge and suctionof periodically operating pumps, particularly peristaltic pumps. 7

Peristaltic pumps are particularly useful in laboratories, as theyenable a relatively simple mechanism to simultaneously generate a streamof a medium in a large number of resilient hoses situated side by side.Similar pumps are very suitable for operation with a segmented stream,that is with a stream of a medium subdivided by pistons (for instancegas pistons) into individual segments. Peristaltic pumps have however anumber of drawbacks which are at present considered irremovable.Primarily they have a certain lack of uniformity of the stream deliverywithin the so called critical range of the pump. The critical rangebeing defined as the area where the occluding organ in its compressiontrack starts to withdraw from the hose and to release it, whereby theocclusion ceases and the hose starts to regain, by its elasticity, itsnormal shape. This condition generates irregularities of the deliveredstream which reduce the otherwise high accuracy of peristaltic pumps.

SUMMARY OF THE INVENTION According to this invention the occluding organmoves within a part of itstrack from the marginal point of occlusion upto the last point of contactwith the hose of the pump opposite to asurface having a longitudinal profile and the distances betweenindividual points from the contact point of the occluding organ change,being reversibly proportional to the speed of advance of the stream ofthe medium required by the program in the individual points of saidtrack.

The invention covers also an arrangement for regulating and programmingthe discharge and the suction of these pumps whereby to a fundamentalsupporting plate, the active surface of which has a constant distancefrom the track of the contact points of the occluding organs, anauxiliary support is joined, the individual points of its active surfacehaving a distance from the contact points of the occluding organ whichchange being reversibly proportional to the speed of advance of thestream of the medium, required by the program in the individual pointsof said track.

The invention provides a peristaltic pump, where the irregularities ofthe stream of the medium within the changes to another value after thepassage of the medium, either stepwise or continuously.

DESCRIPTION OF DRAWINGS The attached drawings show exemplary embodimentsof the prior art as well as of the present invention.

FIG. 1 is a schematic view of a peristaltic pump of known design;

FIG. 2 a schematic view of another known design of a peristaltic pump;

FIG. 3 is a schematic longitudinal sectional view of the active part ofa peristaltic pump adjusted according to this invention;

FIG. 4 is a partial longitudinal sectional view of an alternativearrangement of a peristaltic pump according to this invention;

FIG. 5 is a partial sectional view of a further modification of theperistaltic pump according to this invention; and

FIG. 6 is a diagram schematically showing the occluding organ of aconventional pump at full occlusion of the hose and in the course of itssubsequent release.

DESCRIPTION OF PRIOR ART In order to enable a full understanding of theobject of this invention, two peristaltic pumps of. known design will bedescribed first.

FIG. 1 shows one of the commonly used arrangements of peristaltic pumpswhere a number of occlusion rollers 1, 2, 3, 4 are provided eitherdirectly on arms 5 (one arm is only partly indicated in the drawing)critical range are eliminated and which in additon allows the adjustmentof the stream at the critical area according to a predetermined programof control. Preferably the function of programming is to provide for theuniform advance of the medium, but it is also possible to achieve otherconditions. For instance, it is possible to control the stream of themedium so that'it comes to a stop or even to achieve within a shortperiod of operation a negative speed value (that is a movement in theopposite direction) whereby at least a part of this negative speedtogether with the inlet speed of which arms 5 are supported on arotating shaft 6, or according to an alternative arrangement aresupported on spring loaded rocker levers 7, connected by bolts 8 to arms9 fixed on shafts 6. The rollers in the course of their movement trackabout the shaft 6 and come into contact with an elastic hose 10 havingan infeed and a discharge end. The hose 10 rests on a support 11. Thearcuate shape of the support 11 insures that the rollers, within a partof their track remain in contact with the hose 10 which is therebycompressed so that below the individual rollers a complete occlusion,that is a complete closing of the hose is caused. The support 11 isurged against the rollers byan element 12 generating pressure. In thecourse of rotation of the shaft 6 and thus also of the rollers l, 2, 3',4 the place of occlusion advancescontinuously along the hose at anangular speed corresponding to the angular speed of the shaft jacentbranch of the roller chain, whereafter in part B it recedes from therollers.

FIG. 6 shows the operation of the pump schematically. As seen, eachocclusion organ 1,2,3, travels along a curved path 15 a portion of whichconstitutes the compression track wherein the roller compresses oneportion of the wall of the hose 10 against the opposing wall portion.The depth of compression of roller (e.g. 41) provides an occlusionreserve C since so long as the compression is maintained within thisdepth, occlusion of the hose is maintained. During mainteneance of theocclusion reserve C the hose is segmented by the roller forming aportion 16 behind it and a portion 17 ahead of it and by which the mediais separated. This occlusion reserve is required to insure that a tightseal is made between sections 16 and 17. Further, at the initial stageof compression, the compression of the hose reduces the volume of thehose, thus increasing the pressure of the medium in the hose betweenitself and the next preceeding roller. The moving occlusion organs thuspush the medium conveying a stream of medium to the discharge end alongthe path D.

The rollers, when driven along their path at a constant speed, act toimpart an irregularity to the flow of medium in the conveyed streamwithin the pump range which is detected atthe discharge end of the hose.This irregularity is caused by the action of the roller when it releasesfrom the hose during the course of each individual compression period (aperiod being defined as the distance between successive rollers).Actually, at the moment when the occlusion roller 41 lifts in its trackalong the curve 15 from the hose 10 and the roller 41 first releases theso called occlusion reserve C, that is, as the part of one hose wallwhich is pressed into the opposite one begins to recede and as soon aseach roller recedes so far that the reserve C is liquidated, (noteroller 42), the occlusion stops and the space 16 behind the rollerbecomes connected with the space 17 in front of it, and the hose isrefilled with medium. The point where the occlusion stops, defined aslimit point of occlusion is indicated in FIG. 6 by the letter M. In thecourse of the further movement of the particular roller (positionindicated by 42) along the curve 15, the medium in the hose is no longerconveyed at a uniform speed in direction of the arrow D. As the hosestarts to expand up to the place where the roller just leaves it (pointE at position 43) the medium rushes to fill the increasing volumereducing its forward speed. The range between the limit point M and thecontact point E is referred to as the critical range? and is indicatedby the letter K. In the course of release of the hose 10 suction isgenerated in space 17 acting against the discharge of the medium, sothat the resulting discharge is equal to the difference between thedischarge movement generated by the next succeeding roller and thissuction. The amount ofmedium delivered within this critical range K istherefore reduce in dependence on this suction. Since the speed of backflow into the tube from the discharge is directly proportional to thespeed of the rollers, the suction may even rise to such a value that itssurpasses the medium discharge speed, so that the stream of the mediummay actually be reversed and proceeds in the opposite direction, (i.e.,against the direction indicated by the arrow D). This irregularity isvery inconvenient, particularly if a discharge having uniformproportionality is to be achieved. This proportionality cannot beachieved with known pumps and particularly for purposes which have hosesof different diameters. Up till now this drawback could not be removedand it was particularly this drawback, which caused peristaltic pumps tohave been considered to be not quite accurate. Although it is commonknowledge that their total delivery is uniform, the periodic delivery isnot and so far only the mean values of discharge are considered indetermining capacity.

Various steps have been taken in order to eliminate this undesirablecircumstance, one of which is the use of a clamp 18, commonly called abar" indicated schematically in FIG. 2. The bar is located between thecompression track and the discharge. The clamp 18 is adjustable withrespect to a fixed support 19 and is resiliently pressed against thesupport 19 to cause selected deformation of the hose 10 up to a completeocclusion. The bar is particularly used for a stream of gas such as airsegmented by pistons rather than rollers. If the bar is closed, the airor gas compressed between the closed bar and the next approachingocclusion roller is held until the moment when the bar is liftedandreleases the passage of the medium through the hose 10.

None of the arrangements attempted, not even the bar, could remove theabove irregularities in delivery of the stream within the individualperiods.

It has been of course equally impossible to obtain a programmed, thatis, controlled stream of the medium within the critical range of theperistaltic pump and thus also in the discharge conduit of the pump.

It is therefore an object of this invention to provide a peristalticpump which would enable a uniform advance of the pumped medium.

It is another object of this invention to enable an arbi traryprogramming of the stream of the medium both in the suction and in thedischarge conduit.

DESCRIPTION OF PREFERRED EMBODIMENT FIG. 3 shows one of the simplestarrangements which can be made according to this invention. Rollers 20,21, 22, 23 of a peristaltic pump are arranged at mutual distances L andmove along a straight path 24 which passes over a hose 25 suitablysupported so that the rollers and hose engage in a track ofcorresponding shape. The hose 25 is subsequently deformed from the placeof first contact of the individual roller with the hose'which isindicated in the-drawing asbeing below the roller 20 which has justtouched the upper wall of the hose. This deformation corresponds to theconsecutive change along the direction of movement of the distancebetween the path 24 and the support. The support consists of a basesupporting plate 26, the upper active surface 27 of which is parallelwith the path 24 and at the discharge end an auxiliary support 28 havingrection opposite thereto, that is toward the suction.

- side, the distance d decreases inversely proportional to the speed ofthe stream of the medium required by the program at each of theindividual points of the critical range K. i

In accordance with this invention, the interval of re-' lease K of oneroller is made to extend through the entire length of the dischargestroke L of next succeeding roller. Therefore uniform discharge isobtained.

In the simplest case wherein a uniform discharge of the medium isrequired by the program, it is desirable to shape the upper activesurface 29 of the auxiliary, support 28 so that the speed of the streamis slowed to correspond for instance to the time of supply of the bubblepiston (e.g., bar) at the segmentation point prior to discharge. Thisachieves a uniform speed of the medium behind the segmentation point.Any other shape to control speed according to the requirements of anyprogram is of course equally possible.

What has been said about the discharge branch of the pump can beobviously equally applied in the suction branch if a desired dischargeprogram, such as for instance a uniform suction is required. This caseis indicated in FIG. 3 where an auxiliary support 30 is provided at thesuction end, the upper surface of which is shaped so as the meetrequirements according to the stipulated program. If no programming ofsuction is needed, the auxiliary support 30 may be omitted, so that thepump will have only a single auxiliary support at the discharge end. Theconverse holds true if only suction is programmed.

FIG. 4 shows an alternative arrangement where the auxiliary support 28is adjustable. The auxiliary support 28 rests on set screws 31 which arescrewed in into the body of a supporting plate 26 and joined at itsupper active surface 29 to the corner edge 32 of the supporting plate26. The supporting plate 28 is pressed against the screws 31 by theforce of the spring 33 suspended between a bolt 34 on the auxiliarysupport 28 and a bolt 35 on the supporting plate 26. The spring 33 ispreferably situated in an inclined position with respect to the activesurfaces of the supporting plate 26 and of the auxiliary support 28 sothat it is biased toward both the auxiliary support 28 and thesupporting plate 26 as well as to the set screws 31. In this way thecorner edge 32 need not be covered.

A double arrow F (FIG. 4) indicates the length of the compression track,which each roller has to traverse in order to eliminate the occlusionreserve C (see FIG. 6) that is from the point where the roller mustbegin to lift from compressive position up to the place, where theocclusion ceases. From this point on, which is the limit point M ofocclusion, upt to point E, where the roller just leaves the hose 25, thecomplete release of the hose is effected. This distance, indicated bythe double arrow K is the aforementioned critical range of operation.The length of the distance R for the same pump must be different fordifferent diameters of hoses, since each diameter of hose will createits-own variable suction. The uniform discharge effect of the movingrollers will therefore be influenced by the chosen hose as well as thedistance K.

The adjustability of the auxiliary support 28 and thus also of thelength of the criticalrange K is rather important for modern peristalticpumps which may be designed to pump through a larger number of hoses(for instance up to 28 hoses), the diameters of each of which may bedifferent from theother. It was impossible in the known devices toachieve a proportionality of the discharge in each of the differenthoses. For instance in the design shown in FIG." 2, there is nopossibility of adjustment and therefore no possibility to program, thatis, control the combined effect of discharge and suction within thecritical range. This form of control is enabled only by this invention.Thus one of the main disadvantages of prior peristaltic pumps which hadbeen up to now considered irremovable has in fact been removed. Thatthis improvement is important is due to the fact that differences ofprofiles of hoses for currently used pumps can be rather substantial.Forinstance, hoses range from an internal diameter 0.127 mm up to adiameter 2.80 mm or from an external diameter of 1.56 up to a diameter4.2 mm.

The actual development of suction within the critical range K can beempirically determined with acceptable accuracy. Actually deliveredvolumes created by deformations of hoses having different parameters areregistered. Based on the thus determined curves, it is easy to furtherdetermine the time course of changes of distances d that is the angleand length of the surface 9 from the path 24 within the critical range K(see FIG. 3 and 4). By establishing these determination of changes ofdischarge achieved by the sum of the fundamental discharge effect of theperistaltic pump in combination with the suction effect within thiscritical range can be made so that they would correspond to the givenrequirements of the pump program. So for instance if a perfectuniformity of the stream is desired, or if undesirable sudden changes ofspeed are to be eliminated at places both close to the limit point M ofocclusion or close to the contact point E, it is necessary that thelength of the critical range K is, as far as possible, selected to beequal to the distance L of the occlusion rollers. This condition is notmet by any of the known peristaltic pumps. Another important conditionthat has not been met by the prior art is that the difference betweenthe distance d at the limit point M and the distance d atthe contactpoint E should be different for different profiles of hoses. It has beenheretofore impossible to achieve in practical pumps a uniform stream andeven less a controlled stream of the kind produced by the presentinvention.

FIG. 5 shows another modification of this invention. The auxiliarysupport 28 is in this case joined to the base supporting plate 26 sothat at the place of contact of these two elements there is a suddendrop or step indicated by the reference mark 36. In this arrangement,the roller, for instance roller 23 advances very quickly from aposition, where it still fully occludes the hose 25 with the requiredreserve, to a closely adjacent point, where the occlusion immediatelystops and the hose opens. in this case the length of the track portionF, as indicated in FIG. 4, which the roller must traverse in order toeliminate the occlusion reserve C (FIG. 6) is practically reduced tozero. It is obvious that this step 36 can be achieved in the arrangementaccording to FIG. 4 by asuitable adjustment'of the left set screw 31 sothat the auxiliary support 28 can not only be deviated around the edge32, but may be also shifted perpendiculary to the edge 32.

The auxiliary support 28 can be provided either for each hose alone oras a common support for several hoses. Of course individual adjustingelements can be provided for an entire group of individual hoses eitherof equal or different profiles.

Recently arrangements of most modern multichannel peristaltic pumpsaredesired as automatic analysers, a part of which are just peristalticpumps, which can perform different kinds of analysis. For this purposewholly assembled constructional units are provided, correspondingrespectively to different possible analysis conditions. This inventionis particularly suitable for similar cases, as it is possible to achievewith relatively simple means the most advantageous control even if hosesof rather different diameters are used in each. In such cases theauxiliary support 28 can form a unit in combination with the hosesupporting plate 26, so that no individual adjustment is required.

ln the preceding discussion a type of a pump according to FIG. 2 hasbeen considered, where the occlusion rollers move along a track with astraight active branch. Everything that has been said about this type ofpump holds true for other types of peristaltic pumps, particularly wherethe active part of the roller track is curved, as for instance thecircular track seen according to FIG. 1.

I claim:

1. Controlled peristaltic pump comprising at least one flexible hosehaving a suction end and a discharge end for suction and discharge,respectively, of a liquid medium, supporting means having an activesurface for supporting said hose, compressing means disposed oppositesaid supporting means, movable along a predetermined path and adapted toprogressively compress said hose against said supporting means and togenerate a peristaltic pumping effect, said supporting means ineludingat least a first support member substantially parallel to the pathofsaid compressing'means and a second support member disposed next to saidfirst member, said second support member being adjustable with respectto the predetermined path to selectively vary the distance from saidcompressing means thereby controlling the action of said compressingmeans and the discharge of said liquid medium.

2. The pump as defined in claim 1 wherein the second support member ispivotable with respect to the first support member to meet changingdiameter and thickness requirements of hoses supported by the supportingmeans.

3. The pump as defined in claim 1 wherein the second support member ispivotable around an edge through which it contacts the first supportmember and is perpendicularly adjustable to said edge.

4. The pump as defined in claim 1 wherein the second support member isfreely supported by set screws and provided with spring means acting inan inclined direction with respect to the active surface of thesupporting means and pressing said second support member simultaneouslyagainst the first support member and against said set screws.

5. The pump as defined in claim 1 wherein the active surface of thesecond support member of the support means forms a step at the place ofcontact with the first support member of said support means.

6. The pump as defined in claim 1 wherein said compressing means furthercomprising spaced adjacent members which occlude said hose until a lastpoint of occlusion, and continuing to engage said hose until a lastpoint of contact, the distance between said last point of occlusion andsaid last point of contact being substantially equal to the spacingbetween said spaced adjacent members.

1. Controlled peristaltic pump comprising at least one flexible hosehaving a suction end and a discharge end for suction and discharge,respectively, of a liquid medium, supporting means having an activesurface for supporting said hose, compressing means disposed oppositesaid supporting means, movable along a predetermined path and adapted toprogressively compress said hose against said supporting means and togenerate a peristaltic pumping effect, said supporting means includingat least a first support member substantially parallel to the path ofsaid compressing means and a second support member disposed next to saidfirst member, said second support member being adjustable with respectto the predetermined path to selectively vary the distance from saidcompressing means thereby controlling the action of said compressingmeans and the discharge of said liquid medium.
 2. The pump as defined inclaim 1 wherein the second support member is pivotable with respect tothe first support member to meet changing diameter and thicknessrequirements of hoses supported by the supporting means.
 3. The pump asdefined in claim 1 wherein the second support member is pivotable aroundan edge through which it contacts the first support member and isperpendicularly adjustable to said edge.
 4. The pump as defined in claim1 wherein the second support membEr is freely supported by set screwsand provided with spring means acting in an inclined direction withrespect to the active surface of the supporting means and pressing saidsecond support member simultaneously against the first support memberand against said set screws.
 5. The pump as defined in claim 1 whereinthe active surface of the second support member of the support meansforms a step at the place of contact with the first support member ofsaid support means.
 6. The pump as defined in claim 1 wherein saidcompressing means further comprising spaced adjacent members whichocclude said hose until a last point of occlusion, and continuing toengage said hose until a last point of contact, the distance betweensaid last point of occlusion and said last point of contact beingsubstantially equal to the spacing between said spaced adjacent members.